WOT 24-26mph @4000rpm

[tomschauer]

My 355 which is a 400 without the cockpit runs 31 mph at 4400 rpm. Nice cruise at 3300 /24mph. I imagine its just a bit lighter than the 400.
the merc fuel injected 454's run about 170 unless you push it up near the pins, then it will hit 180. It comes back down instantly when rpms are reduced. As others have mentioned, check your strainers, but it is most likely impellers that need replaced.

[mjk1040]

You mentioned cleaning your exchangers. My I suggest you go to the Sea Flush web sight and watch how they clean and descale your water systems. Won't cost you $200.00 if you buy the Sea Flush unit and some descaler. Mike

[hausherrs]

Source of the post You mentioned cleaning your exchangers. My I suggest you go to the Sea Flush web sight and watch how they clean and descale your water systems. Won't cost you $200.00 if you buy the Sea Flush unit and some descaler. Mike

Thanks Mike. I ordered a kit. It looks like you just attach the kit to the strainer housing, start the motor, and keep it topped off with descaler. Then shut it down and let it sit for 2-4 hours (From the bottle instructions)... Any preferences on descaler?

(Edit) I see that Im supposed to use a shop vac to push the descaler in. Not start the engine.

[mjk1040]

No preference, there are a couples different brands, I got Barnacle Buster brand. If you bought the Sea Flush unit with the snorkel attachment, just mix a five gallon pail up and let it suck it in. Watch the Sea Flush videos. Mike

[hausherrs]

Update. I refuled Saturday. Put about 80 gallons of regular unleaded in. Sunday I took it out. It was pretty windy. Into the wind at WOT I could only get the stb up to 3000 and the port topped out at 3400. And I was running at about 19-20 mph. Temps were the same 180ish.

I have not replaced the fuel filters yet. I ordered them and they are on the way.

Im going to clean the strainers today. And descale the heat exchangers next week.

[mjk1040]

Check the descaler your buying, some of it calls to remove your anodes before introducing the descaler, that means your going to need some plugs too.

[hausherrs]

Check the descaler your buying, some of it calls to remove your anodes before introducing the descaler, that means your going to need some plugs too.

Got it. Do you recall how many there are? I recall seeing two per engine.

[mjk1040]

That seem about right, your engine parts manual should show them all. I think they are in the coolers.

[tonyiiiafl]

I have a 94 390 CPMY with twin Merc Bluewater's carbed. She runs @ 2800 about 14, and 25 GPH and 3300 about 18 @34GPH. I am on plane at 18. 160 T stat, and once up on 3400 it will run all day at 180 degrees with no issues. One has to remember, the heat exchanger has a small interface area! The alarm buzzers are set to chime in at 215, so even running at 200 is nothing to be concerned about, IMHO. As for WOT I hit 4 to 41oo AND top out at 28 to 30. Temp about 190. Cools right down after slowing down. Both new thermostats, and bottom is cleaned. I hope this helps someone. I am the second owner, sadly the first passed last July. He took loving care of this vessel and it shows.

39 cockpit MY.jpg

[hausherrs]

Source of the post I have a 94 390 CPMY with twin Merc Bluewater's carbed. She runs @ 2800 about 14, and 25 GPH and 3300 about 18 @34GPH. I am on plane at 18. 160 T stat, and once up on 3400 it will run all day at 180 degrees with no issues. One has to remember, the heat exchanger has a small interface area! The alarm buzzers are set to chime in at 215, so even running at 200 is nothing to be concerned about, IMHO. As for WOT I hit 4 to 41oo AND top out at 28 to 30. Temp about 190. Cools right down after slowing down. Both new thermostats, and bottom is cleaned. I hope this helps someone. I am the second owner, sadly the first passed last July. He took loving care of this vessel and it shows.

39 cockpit MY.jpg

Thanks for the info. The previous owner told me he serviced the heat exchangers a couple months before I bought it. I decided not to use the $80 bottle of barnacle buster yet. I pulled the caps off the strainers and they are spotless. Ill be replacing the fuel filters on the TBs today but other than that I’ll keep running it. The previous owner said that he had the props "Tuned". Hopefully that just means balanced and straightened.